Capacity Maintenance Ratio Determination Device, Battery System And Electric Vehicle

Abstract

A capacity maintenance ratio determination device includes an impedance measurement unit and a capacity estimation unit. An alternating signal is applied from a signal generator to a battery. Frequency characteristics of AC impedance are calculated by the impedance measurement unit based on a response signal output from the battery in response to the alternating signal. A feature frequency is determined from the calculated frequency characteristics. The capacity estimation unit includes a memory and a determination unit. A correspondence relationship among a temperature of the battery, the feature frequency and a capacity maintenance ratio is stored in the memory. The determination unit determines the capacity maintenance ratio of the battery based on the temperature of the battery detected by a temperature detector, the determined feature frequency and the correspondence relationship stored in the memory.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a capacity maintenance ratio determination device of a chargeable and dischargeable battery, a battery system and an electric vehicle.[0003]2. Description of the Background Art[0004]Degradation of a chargeable and dischargeable battery leads to its lower full charge capacity than its initial (when shipped from a factory, for example) full charge capacity. This causes discharge duration of the battery in a full charge state to be shortened as the degradation of the battery proceeds.[0005]A capacity maintenance ratio, which is a ratio of a present capacity of the battery to a reference capacity, is used as a value representing a degradation level of such a battery. A larger capacity maintenance ratio indicates less advanced degradation of the battery, and a smaller capacity maintenance ratio indicates more advanced degradation of the battery.[0006]The full charge capacity needs to be found...

AI Technical Summary

Benefits of technology

[0012]An object of the present invention is to provide a capacity maintenance ratio determination device capable of accurately determining a capacity maintenance ratio in a short period of time without completely charging / discharging a battery, a battery system and an electric vehicle.

Problems solved by technology

In an actual battery, however, the foregoing integrated capacity is not exactly proportional to the amount of change in the battery voltage.

Therefore, the full charge capacity of the battery cannot be accurately obtained in the remaining capacity display device described in JP 8-179018 A.

This method, however, requires a sufficient period of time for charging / discharging the battery.

In addition, when power failure or the like is taken into consideration, a battery used in a backup power supply, an electric vehicle and so on cannot be completely discharged.

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